In recent years, with the spread of a computer an ink jet printer has been widely used not only in offices but also in houses in order to carry out printing or drawing on paper, film, cloth, and the like.
The method of ink jet recording include a system of discharging droplets by applying a pressure by use of a piezoresistor, a system of discharging droplets by foaming ink with the aid of heat, a system of using ultrasonic waves, or a system of sucking and discharging droplets by use of electrostatic force. As the ink for ink jet recording, an aqueous ink, an oily ink, or a solid (fusing type) ink is used.
Of these inks, the aqueous ink is comparatively superior to the oily ink and solid (fusing type) ink in view of possibility that manufacture, handling property, odor, safety, and the like can be simultaneously satisfied, and accordingly has become the leading ink for ink jet recording at present.
Dyestuffs used for these inks for ink jet recording need high solubility in solvent (ink medium), capability of high density recording, good color hue, excellent resistance to light, heat, air, water, or chemicals, good fixing onto image-receiving materials and resistant to blurring, excellent keeping quality of ink, no toxicity, high purity, and furthermore availability at a reasonable price.
However, it is extremely difficult to search dyestuffs meeting the above-described requirements at high levels. Particularly, excellent color hue and fastness are incompatible with each other in many cases, color materials for magenta or cyan ink that meet all requirements as described above are difficult to acquire, and particularly it is difficult to search for dyestuffs where good magenta or cyan color hue is compatible with light resistance enduring an oxidative atmosphere.
Accordingly, although various dyes and pigments have been proposed for the ink jet already and used indeed, dyestuffs that meet all requirements as described above have not been found out yet in the present state.
Hitherto well known dyes and pigments on which the color index numbers are bestowed are difficult to allow the compatibility of the color hue with the fastness required by the ink for ink jet recording.
Azo dyes derived from aromatic amines and five-membered heterocyclic amines as described in the following patent literature 1 are proposed as dyes improved in fastness. However, since these dyes have unpreferable color hues in yellow and cyan regions, the dyes have a problem of deteriorating the reproducibility of color.
The following patent literatures 2 and 3 disclose inks for ink jet recording aiming at the compatibility between the color hue and light resistance. However, the dyestuffs used in the respective literatures have poor solubility in water in a case where they are used for water-soluble inks. Use of the dyestuffs described in the respective literatures for water-soluble inks for ink jet also introduces a problem in wet heat resistance.
Compounds and ink compositions described in the following patent literature 4 are proposed as a means of solving these problems. In addition, in order to improve the color hue and light resistance, inks for ink jet recording where a pyrazolyl aniline azo dyestuff is used are described (the following patent literature 5). However, these inks for ink jet recording were insufficient in both reproducibility of color and fastness of output images.
When glossy paper used exclusively for ink jet for photographic image was used for recording and stuck in a room, it was further found that the keeping quality of image was remarkably poor in some cases. The present inventor presumes that this phenomenon is due to an oxidative gas in the air such as ozone. Furthermore, although this phenomenon occurs with difficulty by putting the paper into a glass-made picture frame and intercepting a stream of the air, this treatment results in limiting conditions for use.
This phenomenon is particularly noticeable in the glossy paper used exclusively for ink jet for photographic image and presents a serious problem to the present ink jet recording system where the photographic image is one of important characteristics.
Furthermore, it was found that the aqueous ink had a problem of deteriorating readily the discharging properties thereof.
[List of Patent Literatures of Conventional Art]
[Patent Literature 1]
JP-A-55-161856
[Patent Literature 2]
JP-A-61-36362
[Patent literature 3]
JP-A-2-212566
[Patent Literature 4]
JP-T-11-504958 (the term “JP-T” as used herein means a published Japanese translation of a PCT application)
[Patent Literature 5]
JP Application No. 2000-80733
The object of this invention is to provide an ink for ink jet recording that is excellent in discharge stability even after aging the ink over a long period of time, in addition, good in color hue, and excellent in weathering resistance, light resistance, heat stability, and oxidation resistance and a recording method where the ink is used.